In the process of electrophotographic printing, a charge-retentive surface, also known as a photoreceptor, is charged to a substantially uniform potential, so as to sensitize the surface of the photoreceptor. The charged portion of the photoconductive surface is exposed to a light image of an original document being reproduced, or else a scanned laser image created by the action of digital image data acting on a laser source. The scanning or exposing step records an electrostatic latent image on the photoreceptor corresponding to the informational areas in the document to be printed or copied. After the latent image is recorded on the photoreceptor, the latent image is developed by causing toner particles to adhere electrostatically to the charged areas forming the latent image. This developed image on the photoreceptor is subsequently transferred to a sheet on which the desired image is to be printed. Finally, the toner on the sheet is heated to permanently fuse the toner image to the sheet.
One familiar type of development of an electrostatic image is called “two-component development”. Two-component developer material largely comprises toner particles interspersed with carrier particles. The carrier particles are magnetically attractable, and the toner particles are caused to adhere triboelectrically to the carrier particles. This two-component developer can be conveyed, by means such as a “magnetic roll,” to the electrostatic latent image, where toner particles become detached from the carrier particles and adhere to the electrostatic latent image.
U.S. Pat. No. 4,614,165, assigned to the assignee hereof, discloses the general principle of what is known familiarly as “trickle” development. Very briefly, trickle development involves providing two distinct supplies of developer: a main supply, from which the developer unit draws developer for application to the electrostatic latent image, and a second, separate developer supply which is used to replenish the first supply over time. Typically, the two quantities of developer have substantially different ratios of toner to carrier. Over time, the relatively toner-rich developer in the second supply is gradually discharged, or caused to “trickle”, into the first developer supply. This trickling provides a substantially continuous replenishment of toner rich developer, and thereby maintains the effective ratio of toner to carrier within the main developer supply within an optimal range.
In a trickle development system, as a fresh supply of developer is discharged into the housing of the developer unit, it is typically necessary that a similar quantity of surplus developer be discharged from the housing of the developer unit. This surplus or waste material is commonly collected in a waste bottle. An auger contained in a transport tube is often used to transport the waste material through the tube to the waste bottle. The transport tube, with the auger therein, typically extends through a seal in an opening in the waste bottle. Waste material traveling through the transport tube is discharged into the waste bottle through an opening in the tube.
U.S. Pat. No. 5,436,703 shows a trickle development system in which a special spillover barrier is provided at the port from which waste developer material is ejected from the development housing. The barrier defines a predetermined height relative to the developer level to ensure proper maintenance of the desired toner to carrier ratio. U.S. Pat. No. 6,353,722 describes a type of trickle exit port having an auger.
The present disclosure generally relates to an exit port configuration that facilitates a basic design of developer unit being readily adaptable for operating at different speeds.